Extra capacitor(?) on bottom of 400 motherboard?

I recently got a 400.  The last time I had a 400 was probably 30 years ago, so it's been a while.  When I turned the motherboard over, I saw this:

Here's a closeup of the section in question:

I think it's a capacitor and it looks like it's going from POKEY pin 17 (5 V power) to C137 (dunno what that does).  The system seems to run just fine, although I haven't tried any diagnostics other than playing Star Raiders and plugging in a BASIC cartridge, a 410 and loading Invitation to Programming 1.

There was an Atari Service sticker from Carmel, NY on the bottom of the case, so that suggests it's had some work done.  Any ideas what this is for?

Thanks,

-Joe